In a hybrid electric vehicle (HEV) a high voltage battery system may be used to provide power to: a motor to propel the vehicle, a motor to start the engine, a heating, ventilating, and air conditioning system (HVAC), and various other vehicle electrical loads. In the electric drive mode or electric vehicle (EV) mode where the vehicle is propelled solely from the battery power, the battery system is expected to provide as much power as it can to extend the operation of the EV mode in order to achieve the best fuel economy. The transition from the EV mode to the hybrid mode occurs when the vehicle controls, for various reasons, decide to start the engine. This requires additional battery power over that which is required to propel the vehicle in the EV mode. If the battery system does not allow additional power to be used, the driver may feel a loss of driving power, or a “torque hole”, as the vehicle controls take power from the traction motor to start the engine. Alternatively, the vehicle controls can temporarily shut down electrical loads, such as the HVAC system; this is also undesirable from a driver comfort standpoint. Therefore, it would be desirable to have a system and method for controlling a power source in a vehicle, such as a battery, that allows a greater power draw from the power system for a short period of time, such as is necessary to start the engine, so as to avoid a power drop from the traction motor or other vehicle electrical loads.